The present invention relates to a film growth method and a film growth apparatus using plasma. More particularly, the present invention relates to a film growth method and a film growth apparatus for forming magnesium oxide (MgO) films on substrates.
In plasma display panels (PDP in the following), MgO is normally used for the protective films for discharge cells. In general, wet methods like coating and dry methods like vacuum vapor deposition are used for the formation of MgO films. Films formed by the dry methods have film qualities that are superior to films formed by the wet methods. Thus, the use of the dry methods in the formation of the MgO films is more common.
In terms of the dry methods, there is vacuum vapor deposition using an electron gun and sputtering. Since vacuum vapor deposition forms films at higher speeds than the sputtering, it is more commonly used. A film growth speed or rate with vacuum vapor deposition that uses the electron gun depends on output power of the electron gun, but it is generally 20-40 (.ANG./s). If the output power of the electron gun is too great, problems, such as splashing in the tablets, or vaporization material, arise.
On the other hand, when MgO is used for the tablets in radio frequency (RF) ion plating, an operating pressure of 10.sup.-3 to 10.sup.-4 Torr is necessary for generating the plasma. However, since this operating pressure hinders the vaporization of MgO, the film growth speed is reduced. The greater the vacuum is below 10.sup.-4 Torr, the easier it is for MgO to vaporize. On the other hand, there is also the method of reactive film growth using Mg for the tablets. However, there are problems such as film quality being unstable and the oxidizing atmosphere shortening the life of the electron gun with this method.
Incidentally, MgO film growth processes take up a large amount of the time in the PDP fabrication process. However, the film growth speeds are insufficient with the above methods, and they are preventing improvements in PDP productivity.